LEAVES 17 



but they are never compound, lobed, or deeply cut. 

 The leaves of the acrocarpous mosses, those coming 

 under Division A in the Keys, may be divided as rela- 

 tively long and narrow, or short and broad. Those that 

 are relatively long and narrow may be hair-like 

 throughout, or broader at the base and gradually nar- 

 rowed (Plate III, Fig. i), or about the same width 

 throughout and then end in a hair-like tip (Plate III, 

 Fig. 2). The leaves that are relatively short and broad 

 may be ovate (Plate III, Fig. 3), or ovate-oblong (Plate 

 III, Fig. 4), or elliptical (Plate III, Fig. 5), or nearly 

 round (Plate III, Fig. 6). 



The leaves of most of the pleurocarpous mosses, 

 coming under Division B in the Keys, vary less in 

 shape and are less easily seen, as they are so small or 

 so closely folded. Although there are some similar to 

 those described above, the shape that is most common 

 is more or less ovate at the base ending in a straight tip 

 (Plate III, Fig. 7), or in a curved tip (Plate III, Fig. 8). 



The edge of the leaf may be entire or serrate, but in 

 only a very few mosses are the serrations seen without 

 a lens. When the cells along the margin of the leaf 

 differ from those of the rest of the leaf, the leaf is said 

 to be bordered. In the large leaves of Mniuni punc- 

 tatum var. elatum (Plate VI, Fig. 5), the thickened 

 border can be seen like a fine, dark-green line around 

 the leaf. 



Leaves are described as ''crisped" when they be- 

 come crinkled, curled, or twisted in drying. 



